Hi, I am using OpenMPI-1.8.3 built with gcc 4.8.3 and I am using an MPI_Alltoallw call to perform an all to some (or some to all) communication.
In the case in which my task is not sending (or receiving) any data I set the datatype for that send or recv buffer to MPI_DATATYPE_NULL - this works fine with other mpi libraries but fails in openmpi. If I set the datatype to something else say MPI_CHAR - it works fine. I think that this is a bug in open-mpi - would you agree? -- Jim Edwards CESM Software Engineer National Center for Atmospheric Research Boulder, CO
